Large-scale spatial pollution patterns around the North Sea indicated by coastal bird eggs within an EcoQO programme

To categorize the marine environmental health status, the Oslo and Paris commissions have recently formulated Ecological Quality Objectives (EcoQOs) for many ecological features including the contamination of coastal bird eggs with mercury and organochlorines. In this study, we describe spatial and temporal patterns of egg contamination around the North Sea and compared them to the EcoQOs. Concentrations of mercury, polychlorinated biphenyl (I PCB) pound congeners, dichlorodiphenyltrichloroethane (I DDT) pound and derivatives, hexachlorobenzene (HCB) and hexachlorocyclohexane (I HCH) pound isomers were analysed in two tern species (Sterna hirundo and Sterna paradisaea) and Oystercatcher (Haematopus ostralegus) eggs collected between 2008 and 2010 in a total of 21 sites in seven countries surrounding the North Sea. Hg, I PCB pound and HCB were highest in the southern sites, while I DDT pound and I HCH pound concentrations were greatest in eggs from the western North Sea and the Elbe estuary. There were rarely any consistent decreases over time for any compounds. In the terns, Hg, HCB and I HCH pound increased at most sites, I PCB pound and I DDT pound in Sweden and Norway. In the Oystercatcher, HCB and I HCH pound increased at more than the half of the sites, I PCB pound, I DDT pound and Hg at several German sites. In the terns, Hg, I PCB pound and I DDT pound exceeded the EcoQO in all, HCB in most years and sites. At most sites, I HCH pound fulfilled the EcoQO in some study years. In the Oystercatcher, Hg, I PCB pound and I DDT pound exceeded the EcoQO in all or most years and sites. HCB and I HCH pound fulfilled the EcoQO in some or all years at most sites. The EcoQO was exceeded most frequently in estuaries. We conclude that EcoQOs are suitable for drawing contamination patterns of the coastal North Sea in an easily understandable manner, offering the opportunity to harmonize the EcoQOs with coordinated environmental monitoring programmes.